This invention relates to a process for treating a solid surface with two successive distinct treatment liquids in order to improve at least one of the hydrophilicity of the surface, its corrosion resistance, and the adhesion to the treated surface by subsequently applied paints. The solid surface treated is preferably a metallic surface and more particularly a surface of aluminum or one of its alloys that contains at least 50 atomic percent of aluminum, all of these being hereinafter included within the meaning of the word xe2x80x9caluminumxe2x80x9d and, mutatis mutandis, within the meaning of any grammatical variations of this word. The treatment compositions do not require hexavalent chromium but are capable of providing a quality of treated surface as good as that achieved in the past by treatments that did use hexavalent chromium, which is increasingly undesirable because of its adverse environmental impact. The invention is particularly advantageously applicable to provide aluminum evaporators, heat exchangers, and condensers with hydrophilic coatings that have good corrosion resistance and little or no tendency to develop undesirable odors during use.
Although any of the common structural metals can be used in constructing practical heat exchanging surfaces, aluminum and its alloys are among those most often used, because of their high heat conductivity. In heat exchanger surfaces, metals are normally used without any relatively thick protective coating such as a paint or lacquer that would generally be used in other types of equipment made from metals and exposed to corrosive environments, to improve the resistance of the equipment, but any such relatively thick protective coating is avoided in heal exchangers because such a coating would also reduce the efficiency of heat exchange.
During the cooling of hot air, a common use of these heat exchangers, moisture contained as vapor in the hot air condenses and initially forms water drops or beads on the fins of the heat exchanger. If the surface of the heat exchanger fins is not sufficiently hydrophilic, these water beads accumulate on the fin surface and tend to bridge across the small spaces between fins, thereby impeding the air flow between fins and reducing the heat transfer efficiency. The condensed water beads also tend to absorb dust and contaminants in the air, such as carbon dioxide, nitrogen oxides, and sulfur oxides, which can promote corrosion of the underlying aluminum, and because of the capillary forces holding in place water drops that have grown sufficiently large to bridge between adjacent fins, the normal drainage of water away from the fins that would otherwise carry away these absorbed contaminants is substantially reduced. Therefore, the formation of water beads on the fins of an aluminum heat exchanger not only decreases heat transfer efficiency but also can physically damage the exchanger.
In order to achieve a desirable combination of a hydrophilic nature and corrosion resistance on metal, particularly aluminum, surfaces, various coatings and treatments have been tried, but no fully satisfactory result has yet been achieved. A chromate conversion coating without any post-treatment usually has inadequate corrosion resistance and often develops an unpleasant odor and poor hydrophilicity. Silicate coating over a chromate conversion coat has often been used but has not satisfied all users. More recently, biocide protected hydrophilic organic polymer films have been used as post-treatments over chromate conversion coatings. While effective, these have proved to be expensive and difficult to control in some commercial operations.
Major alternative or concurrent objects of the invention are to achieve (i) a combination of adequate hydrophilicity and corrosion resistance, compared with the prior art, while minimizing the use of polluting constituents, particularly chromium, and of highly volatile constituents, particularly organic solvents, with potential toxicity or unpleasant odors for workers, in the treatment compositions, (ii) durability of the hydrophilicity under thermal aging and/or practical use, (iii) avoidance of the development of unpleasant odors during practical use of the hydrophilicized surfaces, (iv) improved corrosion resistance of the treated surface, even if it is not necessarily hydrophilic, and (v) improved adhesion of paints to the treated surfaces. Other objects will be apparent from the description below.
Except in the claims and the specific examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word xe2x80x9caboutxe2x80x9d in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, unless expressly stated to the contrary: percent, xe2x80x9cparts ofxe2x80x9d, and ratio values are by weight; the term xe2x80x9cpolymerxe2x80x9d includes xe2x80x9coligomerxe2x80x9d, xe2x80x9ccopolymerxe2x80x9d, xe2x80x9cterpolymerxe2x80x9d, and the like; the first definition or description of the meaning of a word, phrase, acronym, abbreviation or the like applies to all subsequent uses of the same word, phrase, acronym, abbreviation or the like and applies, mutatis mutandis, to normal grammatical variations thereof; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; chemical descriptions of neutral materials apply to the materials at the time of addition to any combination specified in the description and/or of generation in situ in a combination by chemical reactions described in the specification, and do not necessarily preclude chemical changes to the materials as a result of unstated reaction in the combination; in addition, specification of materials in ionic form means that the materials are supplied to prepare the compositions containing them in the form of one or more soluble substance(s) containing the ions specified and implies the presence in any composition specified to contain ionic materials of sufficient counterions to produce electrical neutrality for the composition as a whole; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counternons that act adversely to an object of the invention; the description of liquid materials as xe2x80x9csolutionxe2x80x9d or as xe2x80x9chomogeneousxe2x80x9d or by any grammatical variations of these terms includes not only true thermodynamic equilibrium solution or homogeneity but also dispersions that are stable enough to avoid any separation into two or more distinct phases readily detectable by unaided normal human vision after storage without mechanical disturbance at 25xc2x0 C. for at least 100, or preferably at least 1000, hours; and the term xe2x80x9cpaintxe2x80x9d and its grammatical variations include any similar materials that might be known by more specialized names such as enamel, lacquer, varnish, shellac, radiation curable coatings, photocurable coatings, primer, top coat, electrodeposited coatings, autodeposited coatings, or the like.
It has been found that, in one major process embodiment of the invention, an effective treatment can be achieved by successive intervals of contact with an initial treatment liquid that comprises water and dissolved, dispersed, or both dissolved and dispersed polymers that include substantial mass fractions of benzene rings that are substituted with at least one oxygen atom and at least one substituted aminomethylene moiety on each ring, followed by treatment with a secondary treatment liquid that comprises water and vanadate anions. Other embodiments of the invention include an article of manufacture comprising a surface treated according to the invention and an extended process including a simple process according to the invention along with other operations that may be conventional per se.
A process according to the invention for treating a solid surface so as to transform it to an improved surface comprises, preferably consists essentially of, or more preferably consists of at least the following consecutive operations:
(I) forming a preliminarily improved surface from said solid surface by contacting said solid surface for an initial treatment time interval at at least one initial treatment temperature with an initial treatment liquid that comprises water and dissolved, dispersed, or both dissolved and dispersed polymer molecules that include substituted benzene rings that have as substituents on each ring (i) at least one oxygen atom and (ii) at least one substituted methylene moiety that in addition to its direct bond to the benzene ring is also bonded to an N-substituted amino moiety;
(II) after completion of the initial treatment time interval, discontinuing contact of the preliminarily improved surface with the initial treatment liquid except for any part thereof that may spontaneously remain adherent on said preliminarily improved surface after completion of separation of the initial treatment liquid from the preliminarily improved surface under the influence of a force that promotes separation of liquid from the preliminarily improved surface at least as strongly as does drainage under the influence of natural gravity and, optionally, rinsing the preliminarily improved surface with water;
(III) forming the improved surface by contacting the preliminarily improved surface as provided from the end of operation (II) as set forth immediately above for a secondary treatment time interval at at least one secondary treatment temperature with a secondary treatment liquid that comprises water and vanadate anions; and
(IV) after completion of said secondary treatment time interval, discontinuing contact of the improved surface with the secondary treatment liquid except for any part thereof that may spontaneously remain adherent on said improved surface after completion of separation of the secondary treatment liquid from the improved surface under the influence of a force that promotes separation of liquid from the improved surface at least as strongly as does drainage under the influence of natural gravity; and, optionally,
(V) rinsing with water the improved surface as provided from the end of operation (IV) as recited immediately above.
Preferably before operation (I) as described above, the solid surface to be modified has been cleaned to remove all foreign matter. Cleaning may ordinarily be accomplished by means known in the art to be suitable for the particular material(s) that constitute(s) the solid surface. For aluminum, conventional commercially available cleaners and deoxidizers are preferably used.
The polymer molecules present in the initial treatment liquid used according to the invention preferably are selected from the group consisting of materials (xcex1) and (xcex2) as defined below, wherein:
(xcex1) consists of polymer molecules each of which has at least one unit conforming to the immediately following general formula (I): 
xe2x80x83wherein:
each of R2 through R4 is selected, independently of each other and independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, from the group consisting of a hydrogen moiety, an alkyl moiety with from 1 to 5 carbon atoms, and an aryl moiety with from 6 to 18 carbon atoms; each of Y1 through Y4 is selected, independently of each other and independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, except as noted further below, from the group consistings of: a hydrogen moiety; a xe2x80x94CH2Cl moiety; an alkyl moiety with from 1 to 18 carbon atoms; an aryl moiety with from 6 to 18 carbon atoms; a moiety conforming to the general formula xe2x80x94-CR12R13OR14, where each of R12 through R14 is selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety, and a phosphoalkyl moiety; and a moiety Z that conforms to one of the two immediately following general formulas: 
xe2x80x83where each of R5 through R8 is selected, independently of each other and independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety, and a phosphoalkyl moiety and R9 is selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxy or polyhydroxy alkyl moiety, an amino or polyamino alkyl moiety, a mercapto or polymercapto alkyl moiety, a phospho or polyphosphol alkyl moiety, an xe2x80x94Oxe2x88x92 moiety, and an xe2x80x94OH moiety,
at least one of Y1 through Y4 in at least one unit of each selected polymer molecule being a moiety Z as above defined; and
W1 is selected, independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, from the group consisting of a hydrogen moiety, an acyl moiety, an acetyl moiety, a benzoyl moiety; a 3-allyloxy-2-hydroxypropyl moiety; a 3-benzyloxy-2-hydroxypropyl moiety; a 3-butoxy-2-hydroxypropyl moiety; a 3-alkyloxy-2-hydroxypropyl moiety; a 2-hydroxyoctyl moiety; a 2-hydroxyalkyl moiety; a 2-hydroxy-2-phenylethyl moiety; a 2-hydroxy-2-alkylphenylethyl moiety; a benzyl, methyl, ethyl, propyl, unsubstituted alkyl, unsubstituted allyl, unsubstituted alkylbenzyl; halo or polyhalo alkyl, or halo or polyhalo alkenyl moiety; a moiety conforming to the general formula xe2x80x94(CxH2xO)YH, where y is a positive integer and x, independently for each of the y CxH2xO units in the moiety, represents 2 or 3; and a sodium, potassium, lithium, ammonium or substituted ammonium, or phosphonium or substituted phosphonium cation moiety; and
(xcex2) consists of polymer molecules each of which does not include a unit conforming to general formula (I) as given above but does include at least one unit corresponding to the immediately following general formula (II): 
xe2x80x83wherein:
each of R10 and R11 is selected, independently of each other and independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, from the group consisting of a hydrogen moiety, an alkyl moiety with from 1 to 5 carbon atoms, and an aryl moiety with from 6 to 18 carbon atoms;
each of Y4 through Y6 is selected, independently of each other and independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, except as noted further below, from the group consisting of: a hydrogen moiety; a xe2x80x94CH2Cl moiety; an alkyl moiety with from 1 to 18 carbon atoms; an aryl moiety with from 6 to 18 carbon atoms; a moiety conforming to the general formula xe2x80x94CR12R13OR14, where each of R12 through R14 is selected from the group consisting of a hydrogen moiety, an alkyl moiety, an aryl moiety, a hydroxyalkyl moiety, an aminoalkyl moiety, a mercaptoalkyl moiety, and a phosphoalkyl moiety; and a moiety Z as defined for material (xcex1) above, at least one of Y4 through Y6 in at least one unit of each selected polymer molecule being a moiety Z as above defined; and
W2 is selected, independently from one molecule of the component to another and from one to another unit of any polymer molecule conforming to this formula when there is more than one such unit in a single polymer molecule, from the group consisting of a hydrogen moiety, an acyl moiety, an acetyl moiety, a benzoyl moiety; a 3-allyloxy-2-hydroxypropyl moiety; a 3-benzyloxy-2-hydroxypropyl moiety; a 3-butoxy-2-hydroxypropyl moiety; a 3-alkyloxy-2-hydroxypropyl moiety; a 2-hydroxyoctyl moiety; a 2-hydroxyalkyl moiety; a 2-hydroxy-2-phenylethyl moiety; a 2-hydroxy-2-alkylphenylethyl moiety; a benzyl, methyl, ethyl, propyl, unsubstituted alkyl, unsubstituted allyl, unsubstituted alkylbenzyl moiety; halo or polyhalo alkyl, or halo or polyhalo alkenyl moiety; a moiety conforming to the general formula xe2x80x94(CxH2xO)YH, where y is a positive integer and x, independently for each of the y CxH2xO units in the moiety, represents 2 or 3; and a sodium, potassium, lithium, ammonium or substituted ammonium, or phosphonium or substituted phosphonium cation moiety;
the phrase xe2x80x9cpolymer moleculexe2x80x9d in the above definitions of materials (xcex1) and (xcex2) including any electrically neutral molecule with a molecular weight of at least 300 daltons.
Ordinarily, primarily for reasons of economy, it is preferred to utilize as materials (xcex1) and/or (xcex2) predominantly molecules which consist entirely, except for relatively short end groups, of moieties conforming to one of the general formulas (I) and (II) as described above. Again primarily for reasons of economy, such materials are generally prepared by reacting homopolymers of p-vinyl phenol, for material (xcex1), or phenol-aldehyde condensation products, for material (xcex2), with formaldehyde and secondary amines to graft moieties Z onto some of the activated benzene rings in the materials thus reacted.
However, in some particular instances, it may be more useful to utilize more chemically complex types of materials (xcex1) and/or (xcex2), for example, molecules formed by reacting a condensable form of a molecule belonging to component (xcex1) or (xcex2) as defined above, except that the molecule reacted need not initially satisfy the requirement for component (xcex1) or (xcex2) that each molecule contain at least one moiety Z, with at least one other distinct type of molecule which is selected from the group consisting of phenols, tannins, novolak resins, lignin compounds, aldehydes, ketones, and mixtures thereof, in order to prepare a condensation reaction product, which optionally if needed is then further reacted with (1) an aldehyde or ketone and (2) a secondary amine to introduce at least one moiety Z as above defined to each molecule, so that the molecule can qualify as material (xcex1) or (xcex2).
Another example of more complex materials that can be utilized as material (xcex1) is material in which the polymer chains are at least predominantly copolymers of simple or substituted 4-vinyl phenol with another vinyl monomer such as acrylonitrile, methacryl-onitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone, isopro-penyl methyl ketone, acrylic acid, methacrylic acid, acrylamide, methacrylamide, n-amyl methacrylate, styrene, m-bromostyrene, p-bromostyrene, pyridine, diallyidimethylammonium salts, 1,3-butadiene, n-bual acbaate, 1-butylamino-ethyl methacrylate, n-butyl meth-acrylate, t-butyl methacrylate, n-butyl vinyl ether, t-butyl vinyl ether, m-chlorostyrene, o-chlorostyrene, 2-chlorostyrene, n-decyl methacrylate, N,N-diallylmelamine, N,N-di-n-butylacrylamide, di-n-butyl itaconate, di-n-butyl maleate, diethylaminoethyl methacrylate, diethylene glycol monovinyl ether, diethyl fumarate, diethyl itaconate, diethylvinyl phosphate, vinylphosphonic acid, diisobutyl maleate, diisopropyl itaconate, diisopropyl maleate, dimethyl fumarate, dimethyl itaconate, dimethyl maleate, di-n-nonyl fumarate, di-n-nonyl maleate, dioctyl fumarate, di-n-octyl itaconate, di-n-propyl itaconate, N-dodecyl vinyl ether, acidic ethyl fumarate, acidic ethyl maleate, ethyl acrylate, ethyl cinnamate, N-ethyl methacrylamide, ethyl methacrylate, ethyl vinyl ether, 5-ethyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine-1-oxide, glycidyl acrylate, glycidyl methacrylate, P-hexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isobutyl methacrylate, isobutyl vinyl ether, isoprene, isopropyl methacrylate, isopropyl vinyl ether, itaconic acid, lauryl methacrylate, methacrylamide, methacrylic acid, methacrylonitrile, N-methylolacrylamide, N-methylol-methacrylarnide, N-isobutoxymethylacrylamide, N-isobutoxy-methylmethacrylamide, N-alkyloxymethylacrylamide, N-alkyl-oxymethylmethacrylamide, N-vinylcaprolactam, methyl acrylate, N-methylmethacrylamide, a-methylstyrene, m-methyistyrene, o-methylstyrene, p-methylstyrene, 2-methyl-5-vinylpyridine, n-propyl methacrylate, sodium p-styrene-sulfonate, stearyl methacrylate, styrene, p-styrenesulfonic acid, p-styrenesulfonamide, vinyl bromide, 9-vinyl carbazole, vinyl chloride, vinylidene chloride, 1 -vinyinaphthalene, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyridine N-oxide, 4-vinylpyrimidine, and N-vinylpyrrolidone.
The following preferences, primarily for reasons of economy, improved corrosion resistance, and/or increased water solubility, apply independently for each perference to the molecules of materials (xcex1) and (xcex2):
each of R2 through R6, R10, R11, W1, and W2, independently for each and from one unit to another in the same or a different molecule, preferably is a hydrogen moiety;
each of Y1 through Y6, independently for each and from one unit to another in the same or a different molecule, preferably is a hydrogen moiety or a moiety Z;
each polymer molecule contains a number of units corresponding to one of general formulas (I) and (II) as defined above that is at least, with increasing preference in the order given, 2, 3, 4, 5, 6, 7, or 8 and independently preferably is not more than 100, 75, 50, 40, 30, or 20;
in the total of materials (xcex1) and (xcex2) in a composition used in operation (II) according to the invention, the number of moieties Z has a ratio to the number of aromatic nuclei that is at least, with increasing preference in the order given, 0.01:1.0, 0.03:1.0, 0.05:1.0, 0.10:1.0, 0.20:1.0, 0.40:1.0, 0.50:1.0, 0.60:1.0, 0.70:1.0, 0.80:1.0, 0.90:1.0, or 0.95:1.0 and independently preferably is not more than, with increasing preference in the order given, 2.0:1.0, 1.6:1.0, 1.50:1.0, 1.40:1.0, 1.30:1.0, 1.20:1.0, 1.10:1.0, or 1.00:1.0; and
in the total of materials (xcex1) and (xcex2) in a composition used in operation (II) according to the invention, the number of xe2x80x9cpolyhydroxy moieties Zxe2x80x9d, has a ratio to the total number of moieties Z in the composition that is at least, with increasing preference in the order given, 0.10:1.0, 0.20:1.0, 0.30:1.0, 0.40:1.0, 0.50:1.0, 0.60:1.0, 0.70:1.0, 0.80:1.0, 0.90:1.0, or 0.98:1.0; for this purpose xe2x80x9cpolyhydroxy moietes Zxe2x80x9d are defined as moieties Z in which at least one of R5 through R8 in the general formulas given above for moieties Z has (i) from 3 to 8, or preferably from 4 to 6, carbon atoms and (ii) as many hydroxyl groups, each attached to one of the carbon atoms, as one less than the number of carbon atoms in the R5 through R8 moiety.
Poly(5-vinyl-2-hydroxy-N-benzyl)-N-methylglucamine is a specific polymer of the most preferred type, which, in the acidic pH range which is preferred as described below, is present at least in part as an ammonium salt.
Independently of other preferences for the dissolved, dispersed, or both dissolved and dispersed polymers that include substantial mass fractions of benzene rings that are substituted with at least one oxygen atom and at least one substituted aminomethylene moiety on each ring and that are present in the initial liquid treatment composition used in a process according to this invention, the mass of the total of all units in these polymers that conform to one of the general formulas (I) and (II) as described above preferably has a ratio to the total mass of the polymers that is at least, with increasing preference in the order given, 0.05:1.0, 0.10:1.0, 0.15:1.0, 0.20:1.0, 0.25:1.0, 0.30:1.0, 0.35:1.0, 0.40:1.0, 0.45:1.0, or 0.50:1.0.
Aqueous solutions, dispersions, or both solutions and dispersions of the polymers that constitute a necessary component of an initial treatment liquid for use in operation (I) as defined above in a process according to this invention can be prepared by means previously known in the art and described in one or more of the following U.S. Patents, the entire disclosures of which, except to the extent that they may be contrary to any explicit statement herein, are hereby incorporated herein by reference: U.S. Pat. No. 5,039,770 of Aug. 13, 1991; U.S. Pat. No. 5,116,912 of May 26, 1992; U.S. Pat. No. 5,266,410 of Nov. 30, 1993; U.S. Pat. No. 5,298,289 of Mar. 29, 1994; U.S. Pat. No. 4,963,596 of Oct. 16, 1990; U.S. Pat. No. 5,068,299 of Nov. 26, 1991; U.S. Pat. No. 4,970,264 of Nov. 13, 1990; U.S. Pat. No. 5,063,089 of Nov. 5, 1991; U.S. Pat. No. 4,517,028 of May 14, 1985; and 4,433,015 of Feb. 21, 1984, all to Lindert et al. However, all of these patents teach the use of solvents as part of the preparation of the polymers desired. It has recently been found that very similar polymers can be made without use of significant amounts of solvents, and polymers of this latter type are preferred for use in an initial treatment liquid used according to this invention. Processes for making this type of polymers are described in detail in U.S. Pat. No. 5,891,952 of Apr. 6, 1999, the entire disclosure of which, except to any extent that it may be contrary to any explicit description herein, is hereby incorporated herein by reference. Some of the pertinent disclosures from this application are set forth below.
Aqueous solutions of such polymers are products of reaction among:
(A) precursor polymer molecules, each of which comprises at least two benzene rings, each of which benzens rings bears at least one substituent moiety that comprises a hydroxyl moiety bonded directly to a carbon atom of the benzene ring;
(B) molecules of at least one material selected from the group consisting of aldehydes and ketones; and
(C) molecules of at least one primary or secondary amine. A process of making such a material comprises the following operations:
(Ixe2x80x2) reacting the phenolic polymer or copolymer, component (A), in water with an organic or inorganic base to form the corresponding phenoxide salt;
(IIxe2x80x2) reacting the aqueous solution from operation (Ixe2x80x2) with the amine, component (C), and the aldehyde, ketone, or mixture thereof, component (B), at a temperature within the range from 20to 100xc2x0 C., preferably from 50 to 80xc2x0 C.;
(Illxe2x80x2) adding an acid to neutralize the base and to react with the amine functionality in the product to solubilize the product; and
(IVxe2x80x2) passing the resulting aqueous solution from operation (IIIxe2x80x2) through an acid cation exchange column in its acid form to exchange cations, such as sodium ions, from the organic or inorganic base. If it is desired to also remove unreacted secondary amine as well, as is normally preferred, a strong acid cation exchange column is preferably used. If it is desired to remove only base cations, a weak acid cation exchange column is preferably used.
The primary reaction in operation (IIxe2x80x2) is believed to be to graft, onto at least some of the benzene rings in component (A), moieties that conform to the first of the formulas for a moiety Z already given above. The moieties R7 and R8 will be those that were in the amine(s) used. Moieties Z that conform to the second of the possible formulas for these moieties already given above may be obtained by oxidation of the first type of Z moiety, for example with hydrogen peroxide, to introduce an xe2x80x94Oxe2x88x92 moiety as R9. In either instance, R5 and R6 will be the moieties attached to the carbonyl carbon in the aldehyde(s) and/or ketone(s) used.
The quantities of components (A), (B), and (C) used to prepare the substituted polyphenol polymer product in aqueous solution are generally from about 0.25 to about 2.0 molecular equivalents of component (B) and from about 0.25 to about 2.0 molecular equivalents of component (C), each based on 1.0 molecular equivalent of benzene rings in component (A). The absolute quantities of these components are selected to provide an aqueous solution from operation (IVxe2x80x2) that contains from 5 to 50, preferably from 15 to 35, % by weight of solids in the solution. Viscosity considerations may of course limit the upper concentration of any particular product.
In operation (Ixe2x80x2) the organic or inorganic base is preferably an alkali metal hydroxide, e.g. sodium or potassium hydroxide, although tetraalkylammonium hydroxides, e.g. tetrabutylammonium hydroxide, or tetraarylammonium hydroxides can also be used. The base shalild be present in at least 10 mole %, and preferably at least 25 mole %, based on *.he phenolic polymer or copolymer.
Operation (Ixe2x80x2) is preferably carried out at a temperature in the range of from 20 to 50xc2x0 C., more preferably from,20 to 25xc2x0 C.
In operation (IIIxe2x80x2) the acid used to neutralize the base can be organic or inorganic. Suitable acids for this purpose include carbonic acid, acetic acid, citric acid, oxalic acid, ascorbic acid, phenylphosphonic acid, chloromethylphosphonic acid; mono-, di- and tri-chloroacetic acid, trifluoroacetic acid, nitric acid, phosphoric acid, hydrofluoric acid, sulfuric acid, boric acid, hydrochloric acid, fluorometallic acids, and the like. The most preferred acids are the fluorometallic acids, specifically fluorosilicic, fluorotitanic, and fluorozirconic acids, with perferences among these acids as specified below.
For operation (IVxe2x80x2), preferred strong acid cation exchange columns are those of the sulfonic acid or phosphonic acid types. Preferred weak acid cation exchange columns are those of the carboxylic acid type.
Component (A), the precursor phenolic or substituted phenolic polymer or copolymer, is preferably selected so as to result after reaction in a preferred type of polymer for the initial treatment liquid as already described above.
The molecular weight of component A can be in the range of 360 to 30,000 or greater. Preferred component (A) is poly (4-vinylphenol) having a molecular weight of from 2500 to 10,000, more preferably from 4,500 to 6,000.
Component (B) is preferably an aldehyde, and most preferably is formaldehyde, especially in the form of paraformaldehyde. Formaldehyde is generally commercially available in a form that contains a significant quantity of methanol, e.g. 15% methanol. Since the present process is carried out in the absence of organic solvents, formaldehyde free from methanol should be used, such as uninhibited aqueous formaldehyde. Paraformaldehyde is also a convenient form of formaldehyde that does not contain any alcohol component.
Component (C) is an amine, preferably a secondary amine, e.g. methylethylamine, dirnethylamine, diethylamine, diethanolamine, dipropylamine, di-n-butylamine, diisoamylamine, dibenzylamine, methyldiethylethylenediamine, methylaniline, piperidine, 1,2,3,4-tetrahydroisoquinoline, 6-methoxy-1,2, 3,4-tetrahydroisoquinoline, morpholine, piperazine, xcex1-methylaminopropiophenone, xcex1-acetylethylbenzylamine; benzyl-(2-cyclohexanonylmethyl)-amine, 3,4-methylenedioxybenzyl-(2-cyclohexanonylmethyl) -amine, N-meihylglucamnine, glucosamine, and t-butylamine; or mixtures thereof. Primary amines, such as C1-C2 alkyl amines and the like, can also be used.
An optional further operation (Vxe2x80x2) can be employed if it is desired, as is generally preferred, to add a fluormetallic acid to the composition. Operation (Vxe2x80x2) is carried out by adding to the composition from operation (IVxe2x80x2) a fluorometallic acid, e.g. fluorotitanic acid (H2TiF6), fluorosilicic acid (H2SiF6), fluorozirconic acid (H2ZrF6), and the like, generally in an amount from about 0.01 to about 5.0% by weight, based on the weight of the final aqueous composition. The solution can then again be passed through an acid cation exchange column.
In an initial treatment liquid used in a process according to the invention, the total mass of dissolved, dispersed, or both dissolved and dispersed polymers that include substantial mass fractions of benzene rings that are substituted with at least one oxygen atom and at least one substituted aminomethylene moiety on each ring preferably constitutes a fraction, referred to the total mass of the initial treatment liquid, that is at least, with increasing preference in the order given, 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, or 0.19% and independently preferably, primarily for reasons of economy, is not more than, with increasing preference in the order given, 10, 8, 6, 4, 2, 1.0, 0.80, 0.70, 0.60, 0.50, 0.45, 0.40, 0.35, 0.30, 0.28, 0.26, 0.24, or 0.22%.
An initial treatment liquid according to the invention preferably has a pH value that is at least, with increasing preference in the order given, 1.0, 1.5, 2.0, 2.3, 2.6, 2.9, 3.1, 3.3, or 3.5 and independently preferably is not more than, with increasing preference in the order given, 6.0, 5.7, 5.4, 5.0, 4.8, 4.6, 4.4, 4.2, or 4.0. Independently, an initial treatment liquid according to the invention preferably contains dissolved substances selected from the group consisting of fluorotitanate anions (i.e., TiF6xe2x88x922), fluorosilicate anions (i.e., SiF6xe2x88x922), and fluorozirconate anions (i.e., ZrF6xe2x88x922). (For purposes of this description, these ions are to be considered present in an initial treatment liquid whenever materials containing these ions, including their corresponding acids, are dissolved in the composition, irrespective of the actual degree of ionization, complex formation, or the like that may occur in the composition.) Among these materials, fluorosilicate ions are less preferred and fluorozirconate ions most preferred. The concentration of these complex fluorometallate anions in an initial treatment liquid used according to the invention preferably is at least, with increasing preference in the order given, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, or 2.2 millimoles of the anions per kilogram of total initial treatment liquid, this unit of concentration being hereinafter abbreviated as xe2x80x9cmM/kgxe2x80x9d and applicable to other materials as well as to these particular anions; independently, the concentration of these anions preferably is not greater than, with increasing preference in the order given, 20, 18, 16, 14, 12, 10, 8, 6, 5.0, 4.5, 4.0, or 3.5 mM/kg.
It has been found that both the pH value preferences and the fluorometallate anions concentration preferences set forth in the immediately preceding paragraph can sometimes be achieved by using acids corresponding to the fluorometallate anions to adjust the pH of neutral precursor compositions that already contain the polymer content required for an initial treatment liquid to be used according to the invention. This is preferred for both convenience and economy. However, if desired, salts containing the anions may be used instead, together with another acid to adjust the pH. Also and independently, if the pH is not at its desired value when an amount of fluorometallic acid that is sufficient to achieve the desired concentration of fluorometallate anions is present in the composition, other pH adjustment agents as known in the chemical arts generally should be added. Agents with a buffering action, such as ammonium bicarbonate, are generally preferred for this purpose.
The temperature of the initial treatment liquid and the surface being treated are both preferably maintained during the initial treatment time interval at a value that is at least, with increasing preference in the order given, 25, 27, 29, 31, 33, 35, 37, or 39 and independently preferably is not more than, with increasing preference in the order given, 90, 80, 70, 65; 60, 57, 55, 53, 51, or 49xc2x0 C. Independently, the initial treatment time interval preferably is at least, with increasing preference in the order given, 5, 10, 20, 40, 45, 50, 55, 60 or 65 seconds and independently preferably is not more than, with increasing preference in the order given, 300, 200, 180, 160, 140, 120, or 110 seconds.
After completion of the initial treatment time interval as described above, the preliminarily improved surface is preferably rinsed with water to remove substantially all of any residual initial treatment liquid on the preliminarily improved surface before it is contacted with the secondary treatment liquid. Whether or not it is so rinsed, however, it preferably is not allowed to dry before being contacted with the secondary treatment liquid.
Preferred secondary treatment liquids to be used in a process according to this invention consist essentially only of water, vanadate ions, and necessary counterions for the vanadate ions. Preferably, these counterions are alkali metal and/or ammonium ions, because most other vanadates are insufficiently soluble in water. Vanadates of any degree of aggregation may be used, but decavanadates are most preferred; sodium ammonium decavanadate with the chemical formula Na2(NH4)4V10O28 is currently most particularly preferred, because it is the least costly commercially available source of decavanadate ions.
The concentration of vanadium atoms present in vanadate ions in a secondary treatment liquid according to this invention preferably is, with increasing preference in the order given, at least 0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.5, 3.0, 4.0, 7, 12, 20, 30, 40, 45, 50, 55, 57, or 59 mM/kg and independently preferably is, with increasing preference in the order given, primarily for reasons of economy, not more than 1000, 500, 300, 200, 150, 120, 100, 90, 80, 75, 70, or 65 mM/kg.
The temperature of the secondary treatment liquid and the surface being treated are both preferably maintained during the secondary treatment time interval at a value that is at least, with increasing preference in the order given, 30, 35, 39, 43, 47, 50, 53, 55, 57, or 59 and independently preferably is not more than, with increasing preference in the order given, 90, 80, 75, 70, 65, 63, or 61xc2x0 C. Independently, the secondary treatment time interval preferably is at least, with increasing preference in the order given, 5, 10, 20, 40, 50, 60, 70, 80, 90, 100, 105, 110, 115, or 119 seconds and independently preferably is not more than, with increasing preference in the order given, 300, 200, 180, 160, 140, 130, 125, or 121 seconds.
After completion of the secondary treatment time interval as described above, the improved surface is preferably rinsed with water, more preferably with deionized or similarly purified water, to remove substantially all of any residual secondary treatment liquid on the improved surface before it is dried or is contacted with any further treatment liquid. The quality of improvement of the surface achieved is not believed to depend significantly on the temperature at which drying occurs, at least if this temperature is between 20 and 100xc2x0 C. However, in order to speed drying rates to a level suitable for normal commercial production speed, when a process according to this invention is being used on a substrate, such as a typical automotive radiator heat exchanger, that has numerous surfaces separated by gap widths of only about a millimeter or less, heat aided drying is normally preferred for reasons of economy. In such instances, a wet improved surface from the end of operation (IV) or (V) of a process according to the invention as recited above preferably is dried by heating to a temperature that is at least, with increasing preference in the order given, 60, 70, 75, 80, 85, 90, or 92xc2x0 C. and independently preferably is not more than, with increasing preference in the order given, 130, 120, 110, 105, 100, or 95xc2x0 C., the heating preferably being continued for an interval of time that is at least, with increasing preference in the order given, 1, 3, 5, 7, 10, 13, 16, or 19 minutes and independently preferably is not more than, with increasing preference in the order given, 60, 50, 45, 40, 35, 30, 25, or 21 minutes. If the improved surface is to be employed for its hydrophilic properties, without the application of any further protective coating, this heating preferably is the next operation after the secondary treatment time interval and any rinsing that follows this time interval. If the improved surface is to be further coated, it may be dried and/or heated immediately, or, if it is to be coated with a water-based protective coating treatment, may be transferred directly to contact with the liquid from which the next protective coating is to be deposited, without being either dried or heated.
Separation of either the initial or secondary treatment liquid, or preferably of both these liquids, used in a process according to the invention normally is preferably aided a by a separation force substantially stronger than that of drainage undernatural gravity. A centrifuge, blowing off with compressed air, or the like is generally employed to reduce the amount of initial and/or secondary treatment liquid that remains on the preliminarily or fully improved surface.